The ribosome is an important example of a multicomponent, macromolecular structure made of ribonucleic acid and many different proteins, whose formation depends primarily on the structure of the interacting molecules. I am particularly interested in determining the comparative primary structure of ribosomal RNA in selected regions of 16S rRNA of prokaryotes and 18S rRNA of eukaryotes to locate conserved RNA sequences which might play a role in protein synthesis. These selected regions are areas of rRNA which are found on the surface of 30S and 40S ribosomes. In general, we do primary structure studies on rRNA to help us understand the role of the ribosome in protein synthesis. We are working with four organisms, 3 prokaryotes, E. coli, A. vinelandii, and B. stearothermophilus, and one eukaryote, Saccharomyces cerevisiae. In the case of the prokaryotes we are concentrating on three parts of 16S rRNA: (1) the 5' end of the molecule, (2) the middle of the molecule, positions 780-850 in E. coli, and (3) the 3' end of the molecule. The latter two regions appear to be at 30S ribosome interface with 50S ribosomes while the 3' end is important for mRNA decoding. The primary structure of the 3' end of 18S rRNA of yeast is similar to the structure of the 3' end of prokaryotic 16S rRNA. Studies are in progress on the conformation of the 3' end of 18S rRNA in 40S ribosomes to determine if there is similarity to the conformation of 16S rRNA in 30S ribosomes.